U.S. Pat. No. 1,731,404 A discloses a flat orifice plate which has a central orifice and which is circular in form and made of MONEL® metal. Entirely surrounding the outer portion of the plate is a gasket member consisting of a cylindrical shell of yielding metal, such as copper, and a yielding material such as asbestos interposed between the side portions of said shell and thus between the adjacent faces of the orifice plate.
U.S. Pat. No. 2,211,247 A discloses a metal gasket with sealing coating, which may be of digested elaterite or some other resilient organic material and works its way into depressions between ridges of the gasket. Upon application of the gasket between cylinder head and block, the resilient coating is squeezed down into the depressions, allowing the high or sharp points of the protuberances to contact the metal of the adjacent elements. These points are then either pressed down or distorted slightly.
U.S. Pat. No. 5,421,594 A discloses a corrugated gasket encapsulated with a graphite material, such as an expanded graphite with adhesive backing.
U.S. Pat. No. 5,785,322 A shows a gasket for flange connections and having concentric deformable ridges.
EP 1995461 A1 discloses leakage prevention in a compressor utilized in a refrigeration cycle. A gasket is formed by covering the two surfaces of a metal plate respectively with rubber layers, and has bead portions formed as projections cresting toward a cylinder block.
U.S. Pat. No. 6,994,356 B2 discloses a gasket seal for flanges of piping and equipment. A sealing ring comprises an outer contour surface, an inner contour surface, a lower surface, and an upper surface. The lower surface and the upper surface, respectively, consist of respective lower and upper prolongations of the outer contour surface and the inner contour surface, and have a serrated profile (concentric grooves) and a sealant coating of a graphite or polymeric material.
In high performance liquid chromatography (HPLC), a liquid has to be provided usually at a very controlled flow rate (e.g. in the range of microliters to milliliters per minute) and at high pressure (typically 20-100 MPa, 200-1000 bar, and beyond up to currently 200 MPa, 2000 bar) at which compressibility of the liquid becomes noticeable. For liquid separation in an HPLC system, a mobile phase comprising a sample fluid with compounds to be separated is driven through a stationary phase (such as a chromatographic column), thus separating different compounds of the sample fluid.
In modern HPLC with pressures rising up to 100 MPa and beyond, life time of components such as seals becomes critical.
GB 2433577 B discloses a gasket for an HPLC instrument having a fluid containing conveying device for receiving and discharging fluids. The device comprises a housing having a chamber for containing a fluid. The housing has a first gasket receiving surface for receiving a gasket. A gasket is formed of a deformable material and has first and second abutment surfaces. The first abutment surface is received on a first gasket receiving surface, and the second abutment surface is received by a chamber closing piece for closing the chamber and having a second gasket receiving surface. At least one of the first and the second gasket receiving surfaces of the chamber closing piece have a retaining groove with at least one edge. Compression means for compressing the gasket are deforming the material such that the gasket is pressed into the retaining groove and gripped by the edge of the cavity to prevent gasket movement.
For sealing valves, filters or the like when being fixed to an HPLC pump head, the applicant Agilent Technologies has introduced a solid gold seal (part number 5001-3707) as disclosed e.g. in GB 1535441 A or under http://www.chem.agilent.com/Library/Support/Documents/A03665.pdf, which has been reliably used over many years.
With increasing pressure of 500-2000 bar as applied in modern HPLC, sealing properties of abutting components in the fluid flow path and in particular seals used between such abutting components become more and more critical.
Therefore, there is a need to provide an improved sealing, in particular suitable for high pressure HPLC applications.